The present invention relates to a high pressure pump. More particularly, the present invention pertains to a high pressure pump that includes an electromagnetic valve that selectively opens and closes a pressurizing chamber defined adjacent to a cylinder in a cylinder body.
Japanese Unexamined Patent Publication No. 8-14140 discloses a high pressure pump that pressurizes fuel supplied to an internal combustion engine. This pump includes a plunger that is located in a cylinder, which is defined in a cylinder body. A pressurizing chamber is defined in the cylinder body adjacent to the plunger. The plunger is reciprocated to pressurize fuel in the pressurizing chamber. An electromagnetic valve is located adjacent to the pressurizing chamber. The valve is controlled to adjust the displacement of the pump.
A washer and a gasket are located between the opening of the cylinder and an end of the electromagnetic valve to seal the pressurizing chamber. The washer and the gasket are tightly held between the body of the valve the opening of the cylinder to so that the pressurizing chamber is reliably sealed. In other words, a relatively high pressure is applied to the opening of the cylinder, which may deform the cylinder. Since the cylinder is machined with a high precision, the deformation increases the friction between the cylinder and the plunger. Also, the orientation of the plunger may be displaced, which prevents smooth motion of the plunger.
To reduce the friction between the inner wall of the cylinder and the surface of the plunger, the clearance between the cylinder and the plunger must be relatively great to compensate for deformation of the cylinder. However, a greater clearance causes liquid to leak from the pressurizing chamber, which lowers the discharge efficiency of the high pressure pump.
Accordingly, it is an objective of the present invention to provide a high pressure pump that reliably seals a pressurizing chamber and improves the displacement efficiency.
To attain the above-mentioned object, the present invention provides a high pressure pump. The high pressure pump includes a cylinder body. The cylinder body has a cylinder and a communication hole communicated with the cylinder. A cover is attached to the cylinder body to surround the communication hole. A plunger reciprocates in the cylinder. An electromagnetic valve has a pressurizing chamber, a valve hole connected to the pressurizing chamber and a valve body for selectively opening and closing the valve hole. The electromagnetic valve is fixed to the cover. When fluid is pressurized in the pressurizing chamber, the valve hole is closed by the valve body and the plunger enters the pressurizing chamber. A seal ring is located between an outer surface of the electromagnetic valve and an inner surface of the communication hole. The seal ring seals the pressurizing chamber.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.